The U.S. embassy in the Central African Republic is resuming operations, 21 months after it closed due to instability and violence.

The announcement from Secretary of State John Kerry came as a new U.N. force, currently with 7,500 troops, officially took over peacekeeping duties in the troubled country.

Kerry named diplomat David Brown as the U.S. charge d'affaires and announced an additional $28 million in humanitarian funding, bringing the U.S. total for the year to $145 million.

The secretary said the C.A.R. has made progress toward ending violence, but added, "We all know that much work remains to be done."

Violence has declined somewhat in recent months as a U.N.-backed transitional government works to restore stability.

More than a half-million people remain displaced from violence that erupted as a mainly Muslim rebel group, Seleka, ousted the C.A.R. president in March 2013. The largely Christian "anti-Balaka" militias subsequently drove hundreds of thousands of Muslims from their homes, with many fleeing to neighboring countries.

The new U.N. peacekeeping force consists largely of African troops already stationed in the country, joined by recent arrivals from Pakistan, Bangladesh and India.

The force is expected to grow to 12,000 in coming weeks, including a 400-member U.N. police force in the capital, Bangui.